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Old 9th August 2002, 08:33 PM   #11
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So Crown has invented the bridged switching amp.

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Old 9th August 2002, 08:49 PM   #12
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Default .1%

Crown claims .1% THD. They have a pretty good reputation so i expect that it really a bit better. Nonetheless, this might be considered a bit high in some audiophile circles where a couple more leading zeroes (.001%) are not un heard up. .1% is probably not audible, but distortions are cummulative and two or three steps in the chain at such a level would get you in to a range that is apearently audible to some. So I would say this is pretty respectable performance for a lot people for a lot of purposes (perhaps a sub woofer amp or a HT system) but it falls short of what some audiophiles would demand.

It's important to keep in mind though that this is much better than PWM amps could previously do. If Crown or some one else can add one or more of those leading zeros (which may well happen eventually) then it would be a whole other ball game.
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Old 9th August 2002, 09:04 PM   #13
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Default THD of "modern" class D

It's important to keep in mind though that this is much better than PWM amps could previously do.
Actually, 0.1% THD is typical for today's class D amps. The Tripath TA0140 evaluation board has a THD of 0.1% into 4 ohms. TACT's digital amplifiers have a reported THD of <0.01% (20 to 20K).

No idea on the veracity of these specs, but these number are what the companies have reported.

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Old 9th August 2002, 11:01 PM   #14
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Default oh

Oh. Nothing like being out of date. .1% is ok but nothing special. Actual 30 years back it would have been more than respectable.

All discussion/comments assume no one is fudging the specs!
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Old 10th August 2002, 12:03 PM   #15
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Personally I use a class-x amplifier - this novel design uses subspace transmutational inductance theory (taking into acount the Hubbel-Einstein constant re-equalisation curve) to convey sound.

It is (when applied correctly) up to 99.9994% efficient and creates a THD of 0.0000003%.

The basic theory is to modulate electro-chemical reactions within the "listener" in accordance with the program content.

The only limitations are of the highly complex filter system used to employ the system - which creates a stop band at the ABBA frequencies to protect the listeners sanity.

Although I may have proven to be of some great insight this knowledge must remain top secret as I am still under obligation to (but no longer working for due to psychotic episodes) NASA.
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Old 12th August 2002, 08:05 PM   #16
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Yeah, I got one of those, but it sounds like crap unless
you are constantly tweaking your chemical intake.
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Old 13th August 2002, 07:32 AM   #17
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Since we are talking about class D amps, have anyone heard ICEPower from Bang & Olufsen? They seem to be the most advanced switched amps today. It's a shame though only OEM customers can buy the amp modules.

Nelson, this modules must be better than Crown, or?
/Per-Anders (my first name) or P-A as my friends call me
PA03 LM4780 amplifier group buy, SIGN UP HERE for the group buy 0 boards left. 118 paid.
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Old 13th August 2002, 08:36 AM   #18
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Hi all

Having developed a class-d amplifier myself a few years ago I'd like to throw in my two pence.

My opinion is that the performance of switching amps will be approaching the performance of conventional amplifiers one day. Though I have a distinct feeling that they will never exceed the performance of the best conventional amps available. But for a majority of people and applications they will be fine (so they will save all the energy wasted by the class-A users )

I was able to listen to two of the best switching amplifiers available today, the Sharp SM-SX100 and the TacT Millennium and I must admit that both sounded excellent. If you have a look at their interiors then you can see how much effort has been put into these (engineering and build, specially the TacT which is an excellent showcase for a well-built piece of equipment).
But I think a conventional amp for the same price sounds equally well.

One thing I like about switching amps is the fact that they are left virtually unimpressed by "difficult" loads. This is true for output signals whose frequency lies well below the output filter's cutoff frequency. For higher frequencies this is an absolutely different story though.

The Crown K-Series is not just a bridged version of a conventional class-D amplifier (JohnMarsh's description is correct in this respect) like Nelson Pass assumed.

It is originally meant to be used for professional P.A. applications. Though a friend of mine once gave them a try and he found them not beeing that useful when used in large quantities within the same rack, because they don't have any fans. Even if they dissipate only about 200 Watts/amp under full load condition this can be quite much if you can't get rid of it. But for applications where there are just a few amps in a rack they will be cool (in every respect).
I was once interested in this amplifier because I am playing the bass-guitar. For this purpose planet10's approach of high-efficiency speaker/low-power amplifier doesn't work that well because speakers that can be moved easily ANDgo really low and loud (not only in their sales brochures !!) aren't that efficient usually.

Though there is a B&O dealer close to the place I work I haven't found the time (or maybe wasn't willing to) audition their Beolab 1 speakers which are making use of their ICE power modules, so I have no idea about their performance so far. But I have studied the patent related to their feedback topology and I must admit that it is quite clever.

If anybody is interested I can try to find the circuit of my class-d amp and scan it. But this might take a few days. It's measured performance wasn't very good at all but we listened to music through it (although not intended for this purpuse !) and it sounded quite pleasing.


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Old 13th August 2002, 09:08 AM   #19
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Default Thermal Advantage

Hi all,

I can see the thermal advantage of making subwoofer amps with CLASS D, but how about the trible and midrange ?

I something gained other than a lot of work building a full range class D amp ?. I mean the thermal stress of a trible amp for active systems is not a problem in consumer systems. (don't know about PA stuff)

I seams to be only the "smaller" 250 W of the B&O models that have full BW.

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Old 13th August 2002, 07:45 PM   #20
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Well, I've read what I can find, including Mr. Marsh's
comments, and I still see bridged PWM amps.

OK, they are synchronized bridged PWM amps, but
apart from that I am sceptical that:

"Crown’s BCA technology creates a totally new paradigm for amplifier design that represents the future of professional amplifiers."
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